Preparation of cuprous chloride electrodes

ABSTRACT

Electrodes for electrochemical cells are prepared from porous copper-containing carrier bodies by immersion at ambient temperature of such bodies in cupric chloride dissolved in an organic non-aqueous solvent such as methanol and subsequently washed in an organic compound capable of dissolving cupric chloride, e.g. methanol to remove excess cupric chloride and then dried in vacuo. The porous carrier bodies may be prepared by sintering arborescent copper powder selected from the group consisting of acicular form or dendritic form having an apparent density of between 1 and 2 first molded to desired shape then heated to about 700* C. in a reducing atmosphere for about one half hour. A conductive copper or copper plated support of metal gauge or perforated metal sheet may be incorporated in the powder during molding. In the alternative the copper carrier body can be molded from such copper powders agglomerated with an organic binder selected from the group consisting of polystyrene, polyethylene and polytetrafluoroethylene and this molded body immersed in cupric chloride dissolved in organic solvent such as methanol, with subsequent washing in organic compound such as methanol to remove excess cupric chloride and ultimate drying in vacuo. Electrodes and electrochemical cells utilizing said electrodes are also described.

United States Patent Gerbier et al.

[ 51 May 9,1972

[54] PREPARATION OF CUPROUS CHLORIDE ELECTRODES [72] Inventors: GerardMarcel Gerbier, Biard; Victor Louis Dechenaux, Poitiers, both of France[73] Assignee: Societe des Accumulateurs Fixes et de Traction (SocieteAnonyme),, Romainville, France 22 Filed: July31, 1970 211 Appl.No.:60,154

[30] Foreign Application Priority Data July 31, 1969 France ..6926329[52] US. Cl ..136/120, 75/200, 117/230, l48/6.14, 156/18 [51] Int. Cl...H0lm 13/08 [58] Field ofSearch ..136/23,83 R, 100 R, 100 M,

[56] References Cited UNITED STATES PATENTS 3,415,687 12/1968 Methlie..136/83 R 3,531,328 9/1970 Bro et a1 ..l36/120 R 2,744,948 5/1956Salauze ..l36/100 R Primary limminer-Winston A. Douglas AssistantExaminer-M. J. Andrews Attorney-Kenyon & Kenyon Reilly Carr & Chapin{57] ABSTRACT Electrodes for electrochemical cells are prepared fromporous copper-containing carrier bodies by immersion at ambienttemperature of such bodies in cupric chloride dissolved in an organicnon-aqueous solvent such as methanol and subsequently washed in anorganic compound capable of dissolving cupric chloride, e.g. methanol toremove excess cupric chloride and then dried in vacuo.

The porous carrier bodies may be prepared by sintering arborescentcopper powder selected from the group consisting of acicular form ordendritic form having an apparent density of between 1 and 2 firstmolded to desired shape then heated to about 700 C. in a reducingatmosphere for about one half hour. A conductive copper or copper platedsupport of metal gauge or perforated metal sheet may be incorporated inthe powder during molding.

Electrodes and electrochemical cells utilizing said electrodes are alsodescribed,

14 Claims, No Drawings PREPARATION OF CUPROUS CHLORIDE ELECTRODESRELATED APPLICATIONS A related application Ser. No. 59,5 14 filed July30, 1970 is copending.

BACKGROUND OF INVENTION The present invention concerns a method forpreparing a cuprous chloride electrode. Such an electrode can be used asa positive electrode in numerous types of electrochemical cells and moreparticularly as a cathode in a primary cell with a lithium anode and anon-aqueous electrolyte.

A method for preparing such an electrode is known through the U. S. Pat.No. 2,744,948 of May 5, 1956 and entitled Primable Electric BatteriesEmploying Cuprous Chloride. This method consists in providing a sinteredcopper carrier which is submitted to the action of a boilingconcentrated aqueous solution of cupric chloride. The metallic copper ofthe carrier then reacts with the cupric chloride to yield cuprouschloride according to the following reaction, which is the reverse ofthe cuprous chloride dis-proportionation reaction:

Although this is, in principle, an equilibrium reaction, experienceshows that if the operation is repeated several times, the originalsintered copper carrier can be very greatly enriched in cuprouschloride, and sometimes even, over enriched, to the detriment of themetallic copper carrier, whose presence as a current collector isnecessary for the proper operation of the electrodes.

Resulting cuprous chloride electrodes can, moreover, contain traces ofmoisture which are difficult to remove, this being another possibledraw-back if they are used in electrochemical cells with non-aqueouselectrolyte, for example, in cells comprising a lithium negativeelectrode.

Objects and features of the present invention are, more particularly, toeliminate the above drawbacks resulting from the practice of the methodof said earlier patent.

Other objects and features of the invention will become apparent fromthe following detailed description by way of illustration but withoutlimitation to the specific details presented.

BRIEF SUMMARY OF INVENTION The invention comprises a method forpreparing a cuprous chloride electrode according to which a porouscarrier containing copper is submitted to the action of a non-aqueousconcentrated cupric chloride solution, characterized in that the saidsolution besides containing no water, is formed by dissolving the cupricchloride in an organic solvent, for example, an alcohol, the reaction ofthe said solution on the carrier being moreover at ambient temperature.

Methanol can, to great advantage, be used as the organic solvent ascupric chloride is very soluble in it (about 680 g per litre at ambienttemperature).

DETAILED DESCRIPTION OF INVENTION EXAMPLE I A methanolic solution ofcupric chloride consisting of a quantity of cupric chloride comprisedbetween 500 and 600 g is dissolved in one litre of methanol.

A porous sintered copper carrier is dipped or immersed in this solutionfor about one-half an hour at ambient temperature. it being possible,however, to extend this immersion time to about three quarters of anhour. The reaction which occurs during the immersion time is as follows:part of the copper forming the original porous metal carrier iscorroded,by the non-aqueous cupric chloride solution to form the activematerial in the form of cuprous chloride in said carrier, thus providingthe desired electrode.

The so-treated electrode is then removed from the nonaqueous solutionand washed by an organic compound capable of dissolving the cupricchloride, for example, methanol, to remove the excess cupric chlorideand then the washed electrode is dried in vacuo.

In the resulting electrode, the copper content of the active material inthe form of cuprous chloride corresponds practically to about twice thecorroded copper of the carrier, since this cuprous chloride comprises asmuch copper derived from the metallic copper as that supplied by thenon-aqueous cupric chloride corroding solution.

By this method of practising the invention, in a single operation, abouta third of the original copper of the original carrier becomes corrodedto cuprous chloride. If this process is repeated by again immersing theelectrode which has already been treated once in said non-aqueousmethanolic solution, the further amount of corroded copper resulting isvery slight. Thus, a repetition of several operational immersion cyclesit is found produces no more than 5 percent of extra cupric chloride.

Thus, the first object of the invention is attained according to whichthe extent of corrosion of the copper content of the carrier to cuprouschloride is limited, although cyclic repetition of immersion can beeffected. This provides a safety margin in production when theelectrodes are required to have a highly conductive metallic carrier.

As only a third of the copper of the carrier has been corroded tocuprous chloride by the procedure electrodes containing practically asmuch copper in metal form as that contained in the cuprous chloridetherein are obtained since about half the cuprous chloride of theelectrode comes from the corroded copper of the carrier and about halfcomes from the copper contained in the non-aqueous cupric chloridecorroding solution.

Moreover, the method of this described example effects attainment of thesecond desired object of the invention, according to which the cuprouschloride electrode contains no water, since during the process, it isnever in contact with any aqueous solution.

Lastly, it should be noted that, in relation to the process described inthe said U.S. Pat. No. 2,744,948 wherein boiling cupric chloride isrequired, the process according to the invention has the advantage ofbeing carried out at ambient temperature.

EXAMPLE II The porous copper carrier to be treated in the manner ofExample I can be made as follows:

Copper powder in arborescent form selected from the group consisting ofdendritic or acicular particles is preferably used, because such apowder has very great entangling qualities, while having a structuresuch that it can easily be corroded by cupric chloride. Relatively lightcopper powders of this type having an apparent density practicallybetween 1 and 2, can be used. Firstly, such powder is molded into therequired shape of the electrode, then the corresponding molded powdercakes are elevated to a temperature of about 700C. for about half anhour in a reducing atmosphere. A suitable conductive support, in theform of metal gauze or of perforated metal sheets, for example, can beincorporated during molding into these electrode shapes, being locatedpreferably in a median plane thereof. These conductive supports mayadvantageously be made of copper, or also can be made of copper-platedsteel.

EXAMPLE III In an alternative procedure, the copper carrier fortreatment in the manner of Example I can be made as follows:

Copper powder of the same kind as in Example II is agglomerated with anorganic binder. This organic binder may be selected from the groupconsisting of polystyrene, polyethlene, or polytetrafluoroethylene. Ineffecting this carrier product, the copper powder and organic binder areagglomerated and molded into desired carrier shape. This shaped carrieris then subjected to the immersion procedure in non-aqueous cupricchloride methanol solution according to the procedure of Example I. Inthe resultant electrode, it has been found that the corroded cuprouschloride fraction of the metal copper in the molded carrier is no longerabout onethird but rather about one-fourth or one-fifth of the metalcopper, thus enabling the production of electrodes having a metalliccarrier of improved conductance.

The electrodes produced by the procedures of any of the Examples are ofutility particularly in electrochemical generators of primary type witha lithium anode and a non-aqueous electrolyte. They are useful, too, inother known types of electrochemical generators with different anodesand electrolytes.

The invention is obviously not limited to specific Examples described,which have been presented only by way of examples. More particularly,details may be modified and certain arrangements may be changed, orcertain means may be replaced by equivalent means, without departingfrom the scope of the invention as defined in the appended claims.

What is claimed is:

l. A method for preparing an electrode for electrochemical generatorscomprising providing a metallic copper containing carrier body,providing a concentrated non-aqueous solution of cupric chloride inorganic solvent, immersing the metallic copper carrier into saidsolution at ambient temperature with resulting corrosive action of thecupric chloride on the metallic copper to provide corrosive conversionof part of the copper metal of the carrier into cuprous chloride, theremaining unconverted metallic copper of the carrier serving as aconductive current carrier for the electrode.

2. A method according to claim 1, wherein said organic solvent is analcohol.

3. A method according to claim 2, wherein said alcohol is methanol.

4. A method according to claim 1, wherein said non-aqueous solutioncomprises cupric chloride and said organic solvent is methanol therebeing approximately 500 to 600 g per liter of cupric chloride dissolvedin each liter of said methanol.

5. A method according to claim 1, wherein said metal copper containingcarrier body is immersed into said nonaqueous solution maintained atambient temperature for from about 30 to 45 minutes.

6. A method according to claim 5 wherein subsequent to immersion in saidsolution, the carrier body is washed in an organic compound capable ofdissolving any cupric chloride existing in excess in the carrier bodyand said body is subsequently dried.

7. A method according to claim 6 wherein said organic compound ismethanol and the drying is effected in vacuo.

8. A method according to claim 1, including the step of preparing theporous metallic copper containing carrier body from copper powder inaborescent form by molding and sintering at elevated temperature in areducing atmosphere.

9. A method according to claim 8 including incorporation into the moldedpowder carrier body ofa conductive support.

10. A method according to claim 9, wherein said support is located in amedian plane ofsaid carrier body, said conductive support being selectedfrom the group consisting of perforated copper and copper platedperforated steel.

11. A method according to claim 1 including the step of preparing themetallic copper containing carrier body by mixing copper powder inarborescent form with an agglomerate and molding to carrier body shape.

12. A method according to claim 11 wherein said agglomerant is selectedfrom .the group consisting of polystyrene, polyethylene andpolytetrafluoroethylene.

13. A method according to claim 11 including incorporation of aconductive metallic support into the carrier body during moldingthereof.

14. A method according to claim 13 including location of the saidsupport in a median pla ne pf the carrier body.

2. A method according to claim 1, wherein said organic solvent is analcohol.
 3. A method according to claim 2, wherein said alcohol ismethanol.
 4. A method according to claim 1, wherein said non-aqueoussolution comprises cupric chloride and said organic solvent is methanolthere being approximately 500 to 600 g per liter of cupric chloridedissolved in each liter of said methanol.
 5. A method according to claim1, wherein said metal copper containing carrier body is immersed intosaid non-aqueous solution maintained at ambient temperature for fromabout 30 to 45 minutes.
 6. A method according to claim 5 whereinsubsequent to immersion in said solution, the carrier body is waShed inan organic compound capable of dissolving any cupric chloride existingin excess in the carrier body and said body is subsequently dried.
 7. Amethod according to claim 6 wherein said organic compound is methanoland the drying is effected in vacuo.
 8. A method according to claim 1,including the step of preparing the porous metallic copper containingcarrier body from copper powder in aborescent form by molding andsintering at elevated temperature in a reducing atmosphere.
 9. A methodaccording to claim 8 including incorporation into the molded powdercarrier body of a conductive support.
 10. A method according to claim 9,wherein said support is located in a median plane of said carrier body,said conductive support being selected from the group consisting ofperforated copper and copper plated perforated steel.
 11. A methodaccording to claim 1 including the step of preparing the metallic coppercontaining carrier body by mixing copper powder in arborescent form withan agglomerate and molding to carrier body shape.
 12. A method accordingto claim 11 wherein said agglomerant is selected from the groupconsisting of polystyrene, polyethylene and polytetrafluoroethylene. 13.A method according to claim 11 including incorporation of a conductivemetallic support into the carrier body during molding thereof.
 14. Amethod according to claim 13 including location of the said support in amedian plane of the carrier body.